When would the relative humidity of an air mass increase?

when the air mass moved from a warm desert over a cold ocean
when water vapor is removed from the air mass and its temperature is increased
when the air mass passes from a cool forested upland to a hot savanna
when water vapor is removed from the air mass but its temperature remains the same
during hours between 7:00 a.m. and 3:00 p.m. on a typical summer day.